1. Field of the Invention
The present invention relates to a device for reducing the emission of noise in buckle folding units provided with sound-proofing enclosures, comprising a noise control hood essentially completely enclosing the upper and lower folding pockets and the folding rolls, said noise control hood being at least partially slidingly displaceable, pivotable and/or removable and being provided with a slot for the passage of the sheet in the associated hood section, which slot is aligned with the nip of the pair of intake and discharge rolls, respectively.
2. Brief Description of the Prior Art
It has already been known to reduce the noise emitted by buckle folding machines by enclosing the whole folding unit or the noise-emitting part thereof, particularly the upper and lower folding pockets, in a noise control hood which, in order to make its interior accessible, is provided with silding, tilting and/or removable parts and which is lined with noise-absorbing and/or noise-reflecting material. However, it is necessary to provide in the associated hood section a slot in alignment with the nip of the intake and discharge rolls, respectively (East German Pat. No. 118,588; "Der Polygraph", Part 20, 1978, pages 1705, 1706).
In view of the fact that trouble frequently arises in the discharge section of the folding unit, such trouble requiring direct access for correction, it has been customary to provide a relatively large aperture on the discharge end. Attempts to dispose part of the noise control hood at the smallest possible distance from the last folding rolls to be passed by the sheets have shown that this remedy makes it very difficult to install and adjust the knives on the knife shafts which are in many cases disposed downstream of the last pair of folding rolls. Particularly in cases in which a plurality of buckle folding units are arranged in series or in which a buckle folding unit is combined with a plurality of knife folding units disposed downstream thereof it may become impossible to dismantle the knife shafts and to remove them from the machine. Also the removal of sheet material which has become jammed in the machine is difficult because such material is not readily accessible.
This disadvantage is found also in the case of a well-known buckle folding machine (West German provisionally laid out print DE-OS No. 23 61 803), the sheet deflectors of which are held to absorb sound conducted through solids. As the noise can be transferred by the rotation of the folding rolls, particularly by the little grooves thereof, sound absorbing or sound dampening bodies are provided between the last two folding rolls and a pair of further shafts which may be installed stationarily. The discharge slot defined by these bodies converges in the direction toward the further shafts. An integration of these bodies in a noise emission control hood is not shown.